The antinociceptive effects of branched-chain amino acids: Evidence for their ability to potentiate morphine analgesia

• Published in: Pharmacology, biochemistry and behavior biochemistry and behavior, 1996-02, Vol.53 (2), p.449-454
• Main Authors: Manner, T., Katz, D.P., Askanazi, J.
• Format: Article
• Language: English
• Subjects: Amino Acids, Branched-Chain - pharmacology; Analgesics; Analgesics - pharmacology; Analgesics, Opioid - pharmacology; Animals; Antinociception; Biological and medical sciences; Branched-chain amino acids; Drug Synergism; Hot Temperature; Hot-plate analgesia test; Male; Medical sciences; Morphine - pharmacology; Neuropharmacology; Pain; Pain Threshold - drug effects; Pharmacology. Drug treatments; Rats; Rats, Sprague-Dawley
• ISSN: 0091-3057; 1873-5177
• DOI: 10.1016/0091-3057(95)02016-0

The effect of branched-chain amino acids (BCAA) on pain threshold was studied in rats. Nociception was induced by the hot-plate analgesia meter, a method measuring supraspinally organized pain responses. After a single intravenous injection of BCAA (320 mg/kg), the percent change in latency time to the pain response significantly increased by 19% in 60 min, and by 22% in 75 min ( p < 0.005), as compared to an injection of an equal volume of a standard concentration of an amino acid solution or physiological saline. Subsequently, we studied the interaction of BCAA with opioid-type analgesia. In combination with intravenously injected morphine (3 mg/kg), BCAA significantly potentiated and prolonged the action of morphine using the hot-plate test. From 5 min after morphine injection, the latencies to a pain response were markedly higher with the combination of BCAA and morphine (+ 80% and + 89% at 5 min after morphine injection, if BCAA was administered 45 or 60 min prior to morphine injection, respectively) when compared with the effect of morphine alone (+ 13% at 5 min; p < 0.005). BCAA demonstrated analgesic effects, which, in combination with morphine, potentiated and prolonged the antinociceptive action of morphine. BCAA may represent a new adjunct treatment modality for acute and chronic pain, and give us further insight into the mechanisms of pain control.